Fig. 3. Fluorescence spectra of P (10 μM) in the presence of different amounts of Al³⁺ (0–10 μM) in ethanol–water solution (9 : 1, v : v, pH 5.8, 20 mM HEPES). Inset: linear fluorescence intensity at 578 nm of P (10 μM) upon addition of Al³⁺ (0.5–9 μM).